Drill grinding fixture combination



Nov. 15, 1955 E. c. CLARKE DRILL GRINDING FIXTURE COMBINATION Filed Aug. 29, 1949 1 8 INVENTOR BY Wu ATTORNEY United States Patent DRILL 'GRINDING FIXTURE COMBINATION Edmund C. Clarke, Orange Park, Fla.

Application August 29, 1949, Serial No. 112,93!) Claims. (c1. 51-219 This invention relates to drill grinding devices and more: particularly to: fixtures of the type sold as an accessory for use with any standard grinding machine.

It is an object. of my invention to provide a device for sharpening, drill points which requires no manual skill or dexterity onv the part of the operator.

It is another object of my invention to provide a device of rugged and simple structure for economical manufacture'. 7

It is a further object of my invention to devise my fixture so that drills sharpened therein are held at precisely the proper positions for efiecting correctly ground lips and point surfaces-i Other objects and features of my invention will be apparent from the description. tofollow.

in general, my invention comprises a drill supporting element, and a drill holding means adapted to clamp around the body of various sizes of drills and to be accommodated inthe supporting element, being accessible for manual rotation, whence the drill isv rotated during grinding, rotation being limited to a 180 arc-by means of certain unique stop elements. The drillholding means is separable from the supporting element and is afii-xed I in proper position to the bodyof the drill by means of a separate gauge provided with and specifically devised for use with a particular supporting element.

The combination of the: three elements outlined above eo-act to properly orient the drill for grinding contact with the side of an abrasive wheel, the supporting element and holding means further co-acting to eliect a precisely and properly sharpened point, all as will now be described in detail in conjunction with the appended drawing in which:

Figure 1 is a side elevation of the supporting body showing the holding means in mid position of rotation thereon,

Figure 2 is a front view of the device,

Figure 3 is a rear view of the holding means,

Figure 4 is a. front view of the holding means,

Figure 5' is a section through 5-5 of Figure 4,

Figure 6 isa section through 6-6 of Figure 1,

Figure 7 is a sectional side view of the gauge for setting a drill in the holder,

Figure 8 is a plan view of the gauge,

Figure 9 is a magnified section through 9-9 of Figure 8, and

Figure 10 is a fragmentary front view of a modified portion of the supporting body.

With reference to Figures 1-6, my invention utilizes a supporting body comprising a base 10 intended to be bolted to a table in suitable juxtaposition to the side of a grinding wheel and a bracket 14 secured to base 10. The base has an. arcuate sector 17 thereon which protrudes through a conforming a-rcuate slot 21 in. bracket '14. Thebracket i's thus supported on the base, being adjustably slidable on. arcuate protuberance 17 and maintained in a selected angular position by a thumb screw and bolt arrangement 24. The slot 21 is on anarc of a ice circle having as its center the apex of the pointof a drill 27 shownin position in the device. Thus any angular adjustment of the bracket M for eifecting a desired grindin g' angle: does not require repositioning of the drill with respect to the grinding wheel, it being assumed that the drill is initially properly set in the device, in a manner to be subsequently described.

Supported on bracket 14' and forming part of a head 28 is a carrier 30 having a horizontal flange 33 by which it is mounted for rotation on a vertical axis and also on a horizontalv axis.

The vertical axis rotation is eftected' e'ccentrically by means of a pin 37 suitably journaled in bracket 14 and about which pin the head is swung during the grinding stroke, and an offset arm 40 secured to the pin 37 and to a. pin 43 which rises from the ofiset arm, passing through a hole 4'5 in flange 33. It will be noted from Figure 1 that bore 45 is enlarged at its ends so that flange 33, which is hinged to pin: 43 by a pintle 4'6- threaded into the flange, may swing clockwise as viewed on Figure 1. The clockwise pivotal motion of flange 33, is arranged so as to be suffieient to carry the point of the drill upwardly and arcuately about pivot 46 and away from the surface of a grinding wheel (not shown). This featureis provided in order to effect maximum control o-fi the device in use when for some reason or other the operator wishes to disengage the drill point from the grinding wheel: at. any time, making for versatility in the sense that various operators prefer to start their stroke in one direction and then resume the stroke in another direction The particular utility of the eccentric: arrangement of pins 37 and 43 is to effect an arcuate motion of the drill point during the grinding, strokein such a manner that the drill. point traversesa path in a direction away from the grinding surface during the grinding stroke rather than into the: grinding surface, thereby diminishing the removal of metal behind the lip of the drill so as to leave a full curved body for support of the lip. The actual eccentricity provided between pins 37 and 43 is quite small and in the particular embodiment shown is approximately a. quarter of an inch, the embodiment being shown full scale on the drawings and being suitable for sharpening drills up to of an inch in diameter. It should be noted that the particular placement of the pins, with relation to each other and to the head 28 is primarily a matter of design within the skill of Workers in the art.

Carrier 30 is formed with V-shaped ways in arm 51 and in the main body portion 54 for slidably supporting a cradle member 57 having a V-shaped channel 60 for rotatively accommodating the drill, the drill being locked therein against endwise movement, in a manner tobe described. Cradle 57 is secured to carrier 30, and moti vated by a screw 63 having an inner end 67 abutting a flange 55 on body portion: 54, a collar 70 being secured near the outer end and abutting on end flange 73 of cradle 57. Thus when the screw is turned by means of a knob 76;, co-action of the screw thread with a thread (not shown) inside an end flange 80' of the carrier serves to reciprocate the cradleand the drill point towards or from the grinding wheel to determine the degreeof metal removed. I

It will be noted that cradle 57 is formed with an interrupted. channel, i. e.,. it is substantially U-shaped so as to provide a recess 81 for accommodating a drill holder or stop-element 82, shown in detail in Figures 3, 4 and 5.

The drill holder comprises a body suitably provided with a rectangular cutout 83' in which is reciprocally slidable a chuck jaw 88 in response to turning of a screw 90 by knob 91, for clamping drill 27 in the holder against a V-shaped formation 93 provided in the holder body at the lower end. It will be noted that the jaw 88 comprises two side pieces, 96 and 99, provided centrally with respective V-shaped formations suitable for clamping drill 27 against the formation 93.

The drill holder is adapted to be supported by the cradle 57 in recess 81 by virtue of being clamped about drill 27 which rests in the V ways of the cradle. Thus drill 27 is locked against endwise motion in the cradle but may be rotated by an operator by merely swinging the drill holder back and forth around the axis of the drill as it rests in the cradle, the drill holder having a smooth sliding fit in the recess.

A particular feature of my invention resides in the coaction of angularly related shoulders 102 and 105, machined into the body of the drill holder, with respective studs 108 and 112 protruding into recess 81 and being integral with the cradle body. Thus, as will be understood from Figure 6, as the drill holder 87 is rocked back and forth about the axis of drill 27, thereby rotating the drill therewith, the studs 108 and 112 will engage the respective shoulders 102 and 105, alternately, to limit the rotation of the drill holder to a 180 are. It will be appreciated that the particular angularity of shoulders 102 and 105 with each other is not necessarily 90 as shown on the embodiment illustrated but depends on the particular spacing between the studs in a specific design. It should be further noted that the rotation between 180 limits is effected regardless of the size of the drill clamped in the drill holder, the shoulders 102 and 105 being of suitable length to engage their respective studs for all drill sizes for which a particular fixture following my teaching is designed.

It will be understood by persons skilled in the art that when a device following my teaching is designed, the layout for the angle of shoulders 102 and 105 and the disposition of studs 108 and 112 is based on 180 rotation of the largest diameter drill with which the device is intended to be used. A simple layout method is to use the axis of such drill as a center on which intersect lines projected from each shoulder plane to the diagonally disposed stud.

Referring now to Figures 7, 8 and 9, I disclose a setting gauge utilized for the purpose of setting a drill properly in the drill holder. The gauge comprises a cradle having spaced V ways 115 and 118 for accommodating drill 27 and holder 82, all as shown in phantom in Figure 7. It will be understood that the drill is first passed between the chuck jaws of the holder 82, being initially loosely held therein, the drill point being thrust up against an end wall the points of entry to one of the flutes are contiguous to the surface of a tapered wall 124 as shown on the enlarged view in Figure 9; this positions the lips of the drill slightly off a vertical line and holds the drill in proper orientation for clamping in the drill holder which is disposed in a rotated position such that the shoulder 105 engages a stud 126 carried by the rear wall 127 of the setting gauge.

Thus, by following the simple procedure just described, the drill will be properly disposed and clamped in the correctly oriented position in the drill holder and this sub-assembly may now be lifted bodily out of the setting gauge and installed in the cradle with the drill resting in the bottom of the V ways as shown in Figures 1 and 2. In this manner the apex of the drill point is correctly positioned to be at the center of the circle of which slot 21 is a sector, as heretofore mentioned.

In conjunction with the drill setting gauge of Figures 7 through 9, it should be noted that the wall 124 tapers inwardly towards the center line of the V ways although it is a plane surface. Thus, in Figure 9, the degree of taper is indicated by the reference character alpha. It will likewise be noted that the front edge of the wall tapers by an angle beta away from vertical. Alpha is empirically determined for proper clearance behind the lip. In the 121. The drill body is then rotated so that particular embodiment illustrated, the angle alpha is approximately 5" although it will be understood that this is purely exemplary and will vary over rather Wide limits in various other designs incorporating the principles taught herein as will be clear to persons skilled in the art.

The angle beta is chosen to accommodate various drill sizes and will be understood to be determined to provide contiguity of the flute corners, only, with the surface of wall 124. This insures disposal of the drill in properly oriented position with respect to the angle desired for the lips in deviating from a vertical plane as shown in Figure 9.

In operation of my device, after the drill has been properly set in the drill holder it is then placed in the cradle with one of the shoulders 102, in engagement with a respective stud, the holder body and knob 91 being in effect a handle for accomplishing this. The entire head is then swung about the pivot pin 43 in a counterclockwise direction, or as viewed in Figure 1, out of the plane of the paper. This motion serves to move the drill point, lip forwardly, in a grinding stroke in contact with the grinding wheel. Thus, as viewed in Figure 9, the lower lip moves to the right it being assumed that the grinding wheel is between the viewer and the plane of the paper. After the lower lip has been sufficiently ground, the drill holder is then rotated or fiipped 180 to the limiting position as determined by the stud 108 as seen on Figure 6 which serves to bring the other lip into the downward, or grinding, position previously occupied by the first lip. Additional counter-clockwise pivoting of the head then effects sharpening of the other lip in the manner heretofore described.

From the foregoing description, it will be obvious that the co-relation of the setting gauge, the drill holder and the pivoted head is such that an unskilled operator cannot help but achieve a properly sharpened drill point with satisfactory clearance and lips ground to the same length. It will be understood that the only operation requiring judgment on the part of an operator is the extent of adjustment of the screw 63 to determine the amount of material removed; I have found that adjustment of the screw to provide a very slight degree of material removal is most satisfactory in the majority of cases. Where, however, a drill has been badly damaged or has been previously improperly ground, larger advances of the cradle are, of course, required.

Figure 10 shows a modification of the fixture in that a cam 130 on bracket 14 is utilized in conjunction with a follower 133 below carrier flange 33. The cam and follower are disposed proximate the forward edges of the bracket and carrier so that as the head is swung the drill point is tilted upward slightly at the beginning of the stroke and then gradually let down as the stroke progrosses. The effect on the drill point will be substantially the same as provided by the eccentric offset arrangement of Figures 1 and 2, hence this modified construction may be used as a substitute therefore, it being noted that a straight pivot pin 137 (and pintle 46) is then utilized intermediate the bracket 14 and flange 133 instead of the offset arm device heretofore described. The use of the cam would be of the order of V inch in the embodiment illustrated.

It will be appreciated that my invention is not limited to the precise embodiment described but may, in fact, be considerably modified without departing from the spirit thereof. Accordingly, I do not seek to limit myself to the specific subject matter disclosed except as set forth in the appended claims.

I claim:

1. A drill grinding fixture comprising support means for supporting a drill for reversible pivotal motion with respect to the surface of a grinding wheel in a predetermined plane with respect to said surface and also for reversible rotary motion about the axis of the drill, a stop means mountable on said drill so as to be carried thereby whereby said drill may be pivoted about its axis by manual actuation of said stop element, said stopelement having engagement means, said support means having engageable means alternately engaged by said stop element engagement means, whereby the pivotal motion of said drill about its axis is limited in clockwise and counterclockwise direction by alternate abutment of the engagement means of said stop element and the engageable means of said support means.

2. A drill grinding fixture comprising an open top cradle having a trough in which a drill may be placed, said cradle having a portion comprising a downwardly dipped recess, a drill holder insertable in said recess and rotative therein and having means for clamping a drill in alignment with said trough whereby said holder is supported in said recess, on said drill, with said drill resting in said trough, said drill holder and said cradle having complementary respective abutment elements engageable as said holder is oscillated from one end to the other of a pre-determined arc about the axis of said drill, and rotative motion means rotatively supporting said cradle for arcuate oscillatory motion on an axis pre-determined relative the face of a grinding wheel, and means for adjustably varying the angle of said axis relative the face of said wheel.

3. In a drill grinding fixture, an open top cradle having a trough to receive and support a drill wherein said drill is rotative in said trough, said trough having a downward dip providing an open top recess for receiving a drill holder, a drill holder, said drill holder having an adjustable clamp for gripping a drill whereby said drill may be secured to said holder and rotated by manual oscillation of said holder, said holder being supported on opposite sides of said recess by said drill, said holder and said cradle having complementary respective abutment elements to limit oscillation of said holder to a predetermined are, including means for rotatively supporting said cradle for rotation about a pre-determined axis relative the face of a grinding wheel.

4. In a drill grinding fixture, an open top cradle having a trough to receive and support a drill wherein said drill is rotative in said trough, said trough having a downward dip providing an open top recess for receiving a drill holder, a drill holder, said drill holder having an adjustable clamp for gripping a drill whereby said drill may be secured to said holder and rotated by manual oscillation of said holder, said holder being supported on opposite sides of said recess by said drill, said holder and said cradle having complementary respective abutment elements to limit oscillation of said holder to a predetermined arc, including means for rotatively supporting said cradle relative the face of a grinding wheel at a plurality of pre-determined angles so as to selectively vary the grinding angle of the point of said drill.

5. In a drill grinding fixture, an open top cradle having a trough to receive and support a drill wherein said drill is rotative in said trough, said trough having a downward dip providing an open top recess for receiving a drill holder, a drill holder, said drill holder having an adjustable clamp for gripping a drill whereby said drill may be secured to said holder and rotated by manual oscillation of said holder, said holder being supported on opposite sides of said recess by said drill, said holder and said cradle having complementary respective abutment elements to limit oscillation of said holder to a predetermined arc, including means for rotatively supporting said cradle for rotation about a predetermined axis relative the face of a grinding wheel, said recess having a wall engageable with said drill holder and serving as a stop, said drill holder having a surface rotatably slidable relative said wall whereby said drill holder may be maintained in substantially the same plane during the course of oscillation by abutment with said wall.

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